To evaluate the possible additive leukocyte count-enhancing properties of lithium and oxymetholone, patients (1-21 years old) were randomized to receive lithium or lithium plus oxymetholone after chemotherapy. Seventy-one trials with lithium, 63 with both drugs, and 79 in the control group, were compared. White blood cell count and neutrophil nadirs were better in both treatment groups than in the controls (p = 0.001) but an additive effect of oxymetholone above and over lithium alone was seen only in patients under 15 years old (p = 0.05). The median duration of severe neutropenia (absolute neutrophil count less than 1000/cm3) was 6.2 days/patient in the control group but only 4.5 days/patient and 3.8 days/patient in the lithium and lithium plus oxymetholone groups, respectively (p = 0.0001). Both the lithium and lithium plus oxymetholone treatments had a modest platelet-sparing effect (p = 0.03). No difference in the hemoglobin nadirs was observed in the three groups. While the majority of the patients lost weight in the control and lithium-treated group, the patients on oxymetholone gained weight (median 1.25 kg) p = 0.00001. Lithium reduces the period of neutropenia after chemotherapy during which the patients may acquire infection. The addition of oxymetholone does not substantially lessen myelosuppression in most patients but improves the patients' appetite and weight.